Powerful nondestructive method for analysis of contrast components in heterogeneous or porous medium is X-ray micro Computed Tomography (XmCT). This technique provides 3D object structure composed of cross-section images of the internal structure with acquisition of grayscale which represents the X-ray absorption distribution (attenuation coefficients) within the object. The idea of correlation between the gray values distribution in X-ray CT image and material densities distribution is described in US Pat. No. 2005/0010106).
Computer tomography technique is based on the interaction of X-rays with material. Passing through an object X-rays will be attenuated depending on the physical density and atomic number of the studied object and on the used X-ray energies. This attenuation information is collected on 2D XmCT image.
Depending on X-ray attenuation coefficient, each point of the black-white slice of object is characterized by different grayness. Because attenuation coefficient depends on material, through X-ray has passed, different materials are characterized by different grayness that allow us to separate individual materials and estimate it's fraction on each X-ray section.
Most widespread method of image recognizing is thresholding. Thresholding is method to separate object of interest from “background” (i.e. other objects) which is based on choosing of optimal threshold level of grayness. All points (“pixels”) of the black-white X-ray image of object which grayness is lower then the threshold value are supposed to belong to object (or background, depending what is more bright).
Special type of this method is histogram based thresholding which is developed for case when an image have only two principal (“dark” and “light”) grayscale regions (see, for example, Gupta L., Sortrakul T. A Gaussian-mixture based image segmentation algorithm. Pattern Recognition, Vol. 31, No. 3, p. 315-325,1998).
Principle disadvantage of thresholding technique is sensitivity of results to selected value of threshold and thus requires a priori information about analyzed parametres.
This invention describes new method which is based on solving of inverse problem while analysis of histogram and provide deterministic solution.